1. Field of the Invention
This invention relates to tube shields and more specifically to tube shields for protecting tubes of boilers and condensers in power plants from highly abrasive and corrosive environments.
2. Description of the Prior Art
Tubes are commonly used in various heat exchanger apparatuses such as boilers and condensers. Tubes employed in boilers are commonly exposed to highly abrasive and corrosive environments. Exposure of these tubes to such environments often has the result of premature failure resulting in expensive maintenance and boiler down-time costs.
Many shield type devices have been devised to protect the tubes from hostile environments. One type of shield device includes an axially elongated protector of arcuate cross section. This device, or shield, is sized to fit over the tube to protect the portion of the tube which it embraces. A strap is then placed around the tube and welded to each side of the shield. This type of shield suffers in that the welds are exposed to the hostile environment and it is difficult to effectuate the weld due to space limitations.
A second method of attaching a common shield to the tubes is to use U-bolts to clamp the shield to the tube. This method requires a U-bolt and flat plate with two holes to bridge the tube and engage the U-bolt. This method is not desirous as the U-bolt is both costly and exposed to the hostile environment.
Another method of attaching such shields to the tubes is to directly weld the shield to the tube. However, because welding can cause unwanted metallurgic changes to the tubes a certified welder is required. In this method the weld is again exposed to the hostile environment which can lead to premature separation of the shield from the tube. These prior art tube shields are disclosed in U.S. Pat. No. 5,220,957 and is hereby incorporated by reference.
A forth method involves a shield which is provided with holes located in appropriate positions such that once the shield is positioned adjacent the tube a rod is simply inserted through the holes to trap the tube therebetween. The rod is subsequently welded to the shield. Here again the weld is exposed to the hostile environment.
A need, therefore, exists for a tube shield which protects a securement weld from the hostile environment of the boiler, and an interlocking tube shield which facilitates easy assembly.